BIRDS IN RELATION TO AGRICULTURE 169 
our forest and shade-trees. The vireos also are unrivalled 
as destroyers of insects which feed on the foliage of trees. 
The swallows and martins scour the air in the search of 
adult insects of all forms, which make up their entire diet. 
Our native sparrows, in which group we do not include 
the undesirable alien house-sparrow, are among the greatest 
weed-destroying agencies, owing to their appetite for weed 
seeds. The song-sparrow is one of our most welcome spring 
arrivals. About three-fourths of its food consists of weed 
seeds and one-fourth of insects. Beetles, especially weevils, 
form the greater portion of the insect food. The chipping 
sparrow, whose confiding ways give it a warm place in our 
affection, is the most insectivorous of our sparrows. About 
42 per cent of its foed consists of insects and spiders, and 
caterpillars make up the major portion of the insect food, 
especially when the young are being reared, when as many 
as seventeen feedings per hour, on an average, for a brood 
of four nestlings, have been recorded. The retiring and 
sombre junco or snowbird destroys insects and feeds on 
weed seeds. An examination of 500 stomachs gave 23 per 
cent animal food (caterpillars, bugs, and beetles), and 77 
per cent vegetable food, of which over 61 per cent consisted 
of weed seeds. In September the proportion of weed seeds 
may rise as high as 95 per cent of the food. 
- Among the commoner weed seeds consumed by the spar- 
rows we find the seeds of bindweed, lamb’s-quarters, rag- 
weed, amaranth, pigeon-grass, etc. Judd records the re- 
sult of the examination of over 4,000 stomachs of twenty 
species of sparrows. It was found that for the entire year 
weed seeds form more than half their food, and during the 
colder months of the year these seeds constitute about four- 
fifths of the food of many species. A single bird will often 
be found to have eaten 300 seeds of pigeon-grass, or 500 
seeds of lamb’s-quarters or pigweed. Beal estimated that 
the tree-sparrow may consume one-quarter ounce of weed 
